Speaker: Jose Carlos Sáez , CIEMAT

Abstract Summary:

J.C. Saez*, E. Correa, D. Burgos, C.Sancho, G.Piña, E. Magro

CIEMAT, Av. Complutense 22, E-28040 MADRID
* Corresponding author: jc.saez@ciemat.es, tel. +34 616978626

Radiological characterization of large areas that could be contaminated with transuranic elements (mainly Pu and Am isotopes) is not an easy task due to the fact that the main emissions from such nuclides are alpha particles. This normally requires complex soil sample designs and the use of radiochemical and alpha spectrometry techniques that are expensive and time consuming. CIEMAT was committed in 2006 to produce in a short time a detailed 3D inventory in an area that could be potentially contaminated with Pu and Am nuclides after a long time. To this aim, different experimental gamma spectrometry designs have been implemented based on the photon emissions of 239+240Pu and 241Am:

• Dynamic measurements by walking over the surface with FIDLER detectors under UniSpec electronics and linked to a Differential Global Position System (DGPS). Data every 2-5 s are recorded and a detailed information is obtained in real time.
• In situ gamma spectrometry in selected locations performed with FIDLER-UniSpec detectors and portable Ge operated under Genie 2K and calibrated with ISOCS.
• Collection of unaltered surface soil samples (up to 15 cm) and boreholes samples (up to 5 m deep) that then are measured in a sample changer device. Two FIDLER detectors are opposed to each end of samples and up to 8 samples can be processed in a single load. Machine operation and gamma analysis are based on Genie 2K.
• HP Ge spectrometry of selected unaltered soil samples and borehole samples based on Genie 2K and ISOCS calibrations.
• Soil sample preparation of thin samples for Low Energy Photon Spectrometry, which yields 241Am concentration and its ratio to 239+240Pu content. The results of these samples are being compared with four independent Alpha Spectrometry labs in order to get confidence to the CIEMAT approach,

All these techniques are based on CANBERRA HS & SW and they have been developed at CIEMAT with the help of TECNASA scientists and technicians. The more practical conclusion is that consistent data are being collected almost in real time, which is highly appreciated by other stages in taking decisions or further sampling designs.